Disc pump

ABSTRACT

A pump is disclosed having one or more rotating discs within a housing. The discs have a plurality of relatively small surface perturbations covering at least half of one side of their surface. The perturbations may be recessed or raised. In operation, a boundary layer is formed near the surface of the rotating discs. The fluid within the pump flows in a circular and outward direction, thus moving fluid from a central coaxial inlet to an outlet located at the peripheral wall of the housing. The surface perturbations produce turbulence within the boundary layer during operation. The pump is suitable for pumping liquids with entrained gases, liquids with entrained solids, liquids with both gases and solids, and thick liquids.

FIELD OF THE INVENTION

The invention relates to a pump, and more particularly to a disc pump wherein the disc or discs have a plurality of surface perturbations covering at least half the surface area of one side of the disc or discs.

BACKGROUND OF THE INVENTION

Boundary layer or bladeless turbines, pumps, and other related turbo-machinery have been known for 100 years or more. Nikola Tesla obtain a patent (U.S. Pat. No. 1,061,142) for such a device in 1913. The Tesla patent disclosed a multiple-disc pump that utilized rotating flat discs with no blades, vanes, or propellers. Such pumps have been referred to as disc pumps, boundary layer pumps, or bladeless pumps.

In related U.S. Pat. No. 1,061,206, Tesla disclosed a fluid-driven boundary layer or bladeless turbine which may be utilized as a prime mover in various applications. The Tesla bladeless turbine, when used as the driving force for a hydro-electric generator, could transform the kinetic energy of a flowing fluid into electrical energy. In U.S. Pat. No. 1,329,559, Tesla disclosed another application of the bladeless turbine, this time in an internal combustion engine. The Tesla patents show early disclosures of rotational machines using bladeless or boundary layer discs.

Unlike more traditional centrifugal pumps which utilize vanes, blades, augurs, buckets, pistons, gears, diaphragms, and the like, boundary layer pumps, such as those described by Tesla, typically utilize multiple rotating parallel discs. Disc pumps, as these machines are sometimes called, utilize the fluid properties of adhesion and viscosity. These fluid properties combine to create an interaction between the fluid and the rotating flat discs that allows the transfer of mechanical energy from the rotating discs to the fluid.

Boundary layer or disc pumps (both name are used in the industry and both will be used interchangeably herein) have been reported to have advantages over more traditional pumps, especially when utilized for pumping fluids other than cool, clean, homogenous liquids. The vanes, buckets, or the like, of traditional pumps wear and lose effectiveness due to normal friction and/or impingement with particles such as sand or other abrasives. However, the flat surfaces of boundary layer pumps are much less susceptible to wear. It is not unusual for such a pump to show little or no wear even after extended use.

Boundary layer pumps have been found to be especially effective for pumping high viscosity fluids wherein the efficiency of such pumps may actually increase as the fluid viscosity increases. Boundary layer pumps have also been reported to be more cost effective in terms of reliability and decreased downtime for pumping problematic multiphase fluids, which may comprise gases, liquids, and/or solid materials. Boundary layer pumps have been found to greatly reduce maintenance costs and downtime when used to replace more traditional pumps in these demanding settings.

Typical vaned centrifugal pumps often require precise gaps between the impellors and the pump housing. When the impellor vanes or blades of such a pump begin to wear, the pump becomes less efficient and may either pump less fluid or produce less outlet pressure, depending upon the application. Disc pumps, on the other hand, are not as dependent upon spacing of the discs. This characteristic is yet another advantage provided by disc pumps over traditional bladed-impellor centrifugal pumps.

Due to the absence of spinning blades or impellers, boundary layer pumps are more gentle on sensitive fluids than are traditional centrifugal pumps. Shear-sensitive fluids or fluids containing fragile or delicate solids may be safely pumped with boundary layer pumps. For example, boundary layer pumps have been used to pump water containing live fish without harming the fish.

Cavitation is another problem that sometimes arises with traditional axial, bladed, centrifugal, and mixed-flow pumps Cavitation describes a vacuum-like condition in the pump which can occur when liquid in the low-pressure area of the pump vaporizes. Vapor bubbles collapse or implode when they reach the high pressure area within the pump. This result can occur due to vapor bubbles formed within the pump, as described above, or due to a mixed-phase fluid entering the pump (i.e. a liquid with entrained gas). Cavitation can create a shock wave powerful enough to damage a pump, other equipment, or connections to the pump or other equipment.

Cavitation is less likely in a disc pump, because the fluid flow changes are more gradual. Much of the flow within a disc pump is laminar, rather than turbulent, which also tends to reduce the risk of cavitation. The pressure differences within a disc pump are typically lower than those seen in bladed-impellor centrifugal pumps, which further reduces the risk of cavitation.

One of the most important advantages of the disc pump is the greatly reduced wear. This advantage is of particular importance when the fluids being pumped contain sand, grit, or other small, abrasive particles. Such a fluid can quickly wear down the impellor blades in a typical centrifugal pump, while the same fluid may cause little or no damage to a disc pump. Another way to explain this distinction is to consider the angle of impingement between the solid particles and the rotating impellor. The higher the angle of impingement (i.e., the closer to 90°) between the particle and the impellor, the greater the damage. In a traditional bladed impellor centrifugal pump, the solid particles impinge the vanes or blades of the impellor at large angles, often close to 90°. In a disc pump, if the solids reach the disc at all, the angle of impingement will be quite low. Because a rotating disc within a disc pump creates a boundary layer, and because the flow in the inner sections of the pump housing is primarily laminar, entrained solids rarely reach the discs, but will instead be gently moved from the inlet to outlet of the pump.

Other problems related to more traditional pumps include vapor lock problems, and pump efficiencies being limited by affinity laws. The flow to head ratio is often restricted by design limitations in traditional pumps. Turbulent flow in the stage to stage transition can be problematic as well.

Traditional centrifugal pumps also produce large axial thrusts. Radial and side loading thrust is often inconsistent relative to rotational speed. Upon startup, up thrust can be detrimental to the ultimate balance of the pump. Not only do these large thrust issues require substantial thrust bearings, but these forces produce wear that leads to greater vibration over time.

Traditional centrifugal pumps are highly subject to vibrations as a natural result of impact of the vanes and blades with the fluids pumped. This vibration problem is highly exacerbated when multiphase fluids are pumped that may include solids, liquids, and gases. Accordingly, the shaft rotation speed of traditional pumps, especially those used for pumping multiphase fluids, is limited to avoid destroying the pump due to vibration damage. The limited shaft rotational speeds result in lower pump output, limited horsepower, and generally less pumping capability.

On the other hand, boundary layer pumps with flat, smooth discs which may be easily balanced and produce little or no vibration when spinning within a fluid even at relatively higher rotational speeds. Typical boundary layer pumps do not utilize lifting surfaces on the rotating elements. Higher rotational speed is directly related to pump flow rates in boundary layer pumps, thus permitting significantly increased pump rotation speeds when pumping multiphase fluids which may contain solids, liquids, and gases. Moreover, boundary layer pumps have been found to not only increase the output under these difficult pumping conditions as compared to traditional pumps, but also have been found to be much more reliable.

Despite the many advantages of boundary layer pumps over more traditional pumps, there remains room for improvement. Many of the disc pumps in use today differ little from the designs disclosed by Tesla over 100 years ago. Flat, smooth discs are typically used. While such discs provide the advantages described above, even greater pump efficiency could be obtained if the boundary layer near the rotating discs were larger or more turbulent. Some variations on flat discs have been disclosed, including ribs or waves extending radially outward on the surface of the discs. These designs may increase the turbulence in the boundary layer, and thus may increase pump efficiency. But these changes tend to move the disc pump closer to the design of the traditional, bladed-impellor centrifugal pump. Adding the equivalent of small blades or vanes on the surface of the discs may improve pump performance in some situations, but it may come at the expense of reliability and longevity. These design variations may also produce a pump less gentle on delicate fluids.

A boundary layer pump that retains the benefits described above while also increasing the pump's efficiency would be a desirable advance over the existing state of the art. To accomplish this result, more turbulence is needed in the boundary layer without significantly changing the low-wear and low-thrust characteristics of the existing boundary layer pump design. The present invention provides such a solution.

SUMMARY OF THE INVENTION

The present invention utilizes a unique design for the discs that makes the pump particularly suited handling multiphase fluids with solids, liquids, and gases. Such fluids are typical of oil and gas wells, geothermal energy production and tar sands oil extraction applications. The invention provides improved pump performance without reducing the long-wear and high-reliability attributes described above. These benefits may be of value in many industrial settings.

The present invention utilizes discs having a plurality of surface perturbations covering more than half the surface of one side of the disc. These surface perturbations may be recessed (e.g., dimples) or raised (e.g., bumps). Each perturbation is small relative to the size of the full disc and is recessed or raised only a small distance. In the embodiments where raised surface perturbations are used, the perturbations protrude only a short distance away from the disc surface and should not, under most operating circumstances, extend beyond the surface boundary layer. Many distinct, yet small, surface perturbations are used to increase the turbulence in the boundary layer near the disc surface and thus increasing pump performance.

In a preferred embodiment, the invention has a generally cylindrical housing formed by a front wall, a back wall, and a peripheral wall, wherein the front wall has a central, coaxial inlet and the peripheral wall has an outlet; a disc having a plurality of surface perturbations, wherein each surface perturbation covers less than 5% of the surface area of one side of the disc and the plurality of surface perturbation collectively cover at least 50% of the surface area of one side of the disc; and, a rotational drive member extending through the back wall of the housing and connected to the disc. Multiple discs having the same or similar surface perturbations may be used, or a single disc may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a disc pump showing multi-phase flow.

FIG. 2 is a perspective, cut-away view of a preferred embodiment of the present invention.

FIG. 3 is a perspective view of a disc having recessed surface perturbations.

FIG. 4 is a cross-sectional view of the disc shown in FIG. 3.

FIG. 5 is a perspective view of a disc having raised, cylindrical surface perturbations.

FIG. 6 is a cross-sectional view of the disc shown in FIG. 5.

FIG. 7 is a perspective view of a disc having raised, hemispherical surface perturbations.

FIG. 8 is a cross-sectional view of the disc shown in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

A cross section of a typical boundary layer or disc pump 10 is shown in FIG. 1. The portion of interest for this description is seen on the right end of the drawing. A pump housing 12 is formed by a front wall 14, a back wall 18, and a peripheral wall 20. These three walls may be distinct pieces or two or more of the walls may be a single part. The three walls are defined in this way based on the physical configuration of the pump housing. This definitional choice is not meant to limit the type of housing in any way. It is for convenience only.

The pump 10 has a inlet 16 located near the center of the front wall 14. The inlet 16 is aligned with the longitudinal axis of the pump drive shaft 32. The inlet 16, therefore, can be described as a central, coaxial inlet. The inlet 16 can take various forms. It can supply feed flow from one side of the housing 12 or from both sides of the housing. A design showing dual inlet flow from both sides of the housing is disclosed in U.S. Pat. No. 4,403,911, which is hereby incorporated by reference. FIGS. 16 and 17 of the '911 patent, and the accompanying description, show a central, coaxial inlet attached to both sides of a pump housing. The only limitation on the inlet is that it be a central, coaxial inlet. One means of providing such an inlet is shown in FIG. 1. Another is shown in the '911 patent.

The housing 12 has an outlet 22 that is positioned on or within the peripheral wall 20. The housing 12 is of a generally cylindrical shape, and the peripheral wall 20 forms the outer surface of the cylinder. In general, the peripheral wall 20 is at a fixed radius from the axial center of the housing 12. The outlet 22 may be formed in a variety of ways, but must be located at or near the radially outermost region of the housing 12. The reason for the locations of the inlet 16 and outlet 22 will be explained in more detail below.

A first disc 26 and a second disc 28 are also shown in FIG. 1. The first disc 26 is shown near the back wall 18 and is operatively connected to the drive shaft 32. Any type of rotational drive member may be used to rotate the discs. A drive shaft 32 is perhaps the most common type of rotational drive member and is, therefore, shown in FIG. 1. A cylindrical drive member or any other type of rotational driving structure may be used. The drive shaft 32 in FIG. 1 is shown threaded into the first disc 26. No particular connection means is required. All that is required is that the rotational driving member be operatively connected to the first disc 26 such that the disc may rotate within the housing 12.

The second disc 28 is shown near the front wall 14. The two discs are connected by pins 30, though other connections are also contemplated. The connecting members between the discs must be of sufficient strength to allow the first disc 26 to cause the second disc 28 to rotate. If additional discs, or additional pairs of discs, are used, similar connections would be required between those discs. Only the first disc 26 is directly connected to the rotational drive member in FIG. 1, though it is contemplated that in some embodiments the rotational drive member may extend into the housing and be directly connected to other discs, as well.

The pins 30 or other members used to connect the discs to each other should be of relatively small cross section in order to reduce the turbulence caused by the rotation of such members through the housing 12 during operation of the pump. To reduce the turbulence induced by such rotation of the connecting pins 30, the pins could be formed in a tear drop or other more aerodynamic form that would reduce the fluid turbulence caused when the pins 30 are rotated through the fluid to be pumped.

To be clear, the front wall 14, back wall 18, and peripheral wall 20 need not be physically distinct components or pieces. For example, the pump 10 of FIG. 1 could be constructed such that the back wall 18 is part of the main body of the pump, with the threaded end of the drive shaft 32 extending through a central opening in the back wall 18. The first disc 26 (or a pair of preconnected discs 26, 28) could then be threaded onto the drive shaft 32. A single physical piece—i.e., a piece comprising the front wall 14, inlet 16, peripheral wall 18, and outlet 22—could then be connected to the back wall 18, thus forming the housing 12 around the discs 26, 28. Alternatively, the back wall 18, peripheral wall 20 and outlet 22 might be a single physical piece, allowing for disc installation, followed by installation of the front wall 14, with inlet 16, to complete the formation of the housing 12. Gaskets or other material to ensure the housing 12 is watertight are not shown, but may also be used as needed. These and other variations are within the meaning of the housing and its three walls as described herein.

The pump 10 shown in FIG. 1 is of a type known in the art. The first disc 26 and second disc 28 are flat and smooth. In operation, the drive shaft 32 is rotated by some driving force, and thereby rotates the discs 26, 28 within the housing 12. For purposes of explaining the operation of the pump, assume the housing 12 is filled with water. When the discs 26, 28 begin to rotate, a thin boundary layer of water near the outer surface of the discs 26, 28 will also begin to rotate. The adhesion of the water (or other liquid) to the solid surface of each disc creates drag, and that tends to pull a thin boundary layer of water along with the disc as it rotates. The two discs 26, 28 shown in FIG. 1, therefore, each cause a thin boundary layer of water to begin rotating in the same direction as the discs.

In the region between the discs, it is the viscosity of the fluid that accounts for the generation of flow. The liquid between discs 26, 28 of FIG. 1 may be understood as many thin sheets of liquid, where each thin sheet is parallel to the two rotating discs. Moving away from the discs 26, 28 and toward the center of the housing 12, we first encounter the thin boundary layers that are rotating in the same direction as the discs 26, 28 due to the adhesion forces between the discs 26, 28 and the boundary layers. The next thin layers of water are in contact with the boundary layers, and due to the viscosity of the water, these next layers of water will begin to rotate with the boundary layers. Each thin layer of water begins to rotate because the water immediately around it is rotating. This process continues until all the water in the housing 12 is rotating in the same direction as the discs 26, 28.

The pump 10, thus produces primarily laminar liquid flow. The boundary layer will experience some turbulent flow due to minor irregularities upon the surfaces of the discs 26 and 28, but the many thin layers of water (as described above) will each rotate primarily in a laminar matter. This is important, because it results in minimal mixing of the liquid within the housing. If there were perfectly laminar flow within the housing, there would be no impingement of solid particles with the discs, because such particles would remain fixed within their respective layer of laminar flow. Though this ideal scenario does not occur in practice, the prevalence of laminar flow does greatly reduce the impingement of particulates with the discs.

As the water in this example rotates with the discs, the water experiences centrifugal forces which tend to force the water radially outward from the axial center of the housing 12. The water, therefore, moves in a generally outward spiral from the axial center to the outer peripheral region of the housing 12, where the outlet 22 is positioned. Because of the process described above, the water (or other liquid) is pumped from the central, coaxial inlet 16 to the outlet 22. In FIG. 1, the liquid entering the pump 10 has entrained gas or solid particles 24, which are moved in the same outward spiral pattern as the liquid. The entrained matter 24 moves through the pump housing 12 with little, if any, contact with the rotating discs 26, 28.

The disc pump 10 described above may use a single rotating disc, a pair of discs (as shown in FIG. 1), or a larger number of discs, which may be arranged in pairs or as a series of individual discs. If a single disc is used in a relatively large housing, the pump will not generate as large a pump head as it would if multiple discs are used. For example, if only the first disc 26 of FIG. 1 were used, the pump would work, but the liquid nearest the front wall (i.e., the farthest from the first disc 26) would receive the least rotational force. The single disc pump may produce a lower pump head, lower flow rate, or both. Use of a pair of discs, as shown in FIG. 1, or use of even more discs, is generally preferred to use of a single disc if a large flow rate or pump head are required.

On the other hand, a single disc pump is the most gentle embodiment of the present invention. When two or more discs are used, connecting pins 30, or some other connecting members, may be used to connect the discs together. These pins 30 or other connecting members rotate with the discs, causing some turbulence within the housing 12. Moreover, the rotation of connecting pins 30 can result in damage to particles or other materials impacted by the pins 30 as the discs 26 and 28 rotate. When the most gentle pumping is required, a single disc pump may be the best option. Examples of situations where this may be appropriate might include pumping of live fish or fragile solids suspended in a liquid.

A preferred embodiment of the present invention is shown in FIG. 2, which is a perspective view of a cut-away of a disc pump 10. There is a housing 12 formed by a first wall 14, second wall 18, and peripheral wall 20, just as explained above with respect to FIG. 1. The central, coaxial inlet 16 and the outlet 22 are also shown in a manner similar to the configuration of FIG. 1. A first disc 26, second disc 28, and connecting pins 30 are also shown, as is a drive shaft 32. A thrust bearing assembly 34 and a shaft seal assembly 36 are also shown for illustration purposes.

The inner surface of the first disc 26, as shown in FIG. 2, is covered with small, recessed dimples 38. These dimples 38 are also present on the inner surface of the second disc 28, but cannot be seen due to the perspective presented in FIG. 2. The dimples 38 create a markedly different result when the discs rotate, as compared to the description provided above.

When the dimpled discs shown in FIG. 2 rotate through the liquid, the many dimples create small surface disturbances in the liquid near the disc surfaces. Small eddy currents are formed as liquid enters and leaves the many dimples 38. Each dimple 38 is small and shallow, and thus creates only a very small disturbance to the liquid near the disc surface. The collective impact, however, of many such small disturbances is a substantially more turbulent flow within the boundary layer. This turbulence may also produce a thicker boundary layer.

The more turbulent boundary layer is more adherent to the disc surface, and this increase in the adhesion force results in more rotational movement of liquid within the boundary layer. As the boundary layer rotates faster, each thin layer of water moving toward the center of the housing 12 also rotates faster. When a thicker boundary layer is formed, more liquid is impacted by the adhesion force, and thus more liquid movement results. By creating a more turbulent boundary layer, the discs of the present invention create more flow and a larger pump head as compared to a traditional disc pump with smooth flat discs.

Recessed dimples 42 are shown in more detail in FIGS. 3 and 4. More than half of the surface of the disc 40 is covered with dimples 42 in FIG. 3. In a preferred embodiment, 70% or more of the disc surface 40 is covered. Each dimple 42 is small relative to the full disc surface 40. Indeed, each dimple 42 covers an area that is less than 5% of the surface of the side of the disc. Many dimples 42 are needed to cover at least half (i.e. 50% or more) of the surface of one side of the disc. In a preferred embodiment, the dimples 42 are only on one side of the disc, though a disc positioned at an intermediate point within the housing 12 might have dimples on both sides and thus be used to produce flow on both sides of the disc.

FIG. 4 shows a cross section of the disc surface 40. Many dimples 42 are shown. In a preferred embodiment, the dimples 42 have a depth 44 equal to roughly (i.e., approximately)50% of the thickness of the disc. This depth 44 is not critical to the performance It does provide, however, for a deep enough dimple to produce surface turbulence while also allowing the disc to retain structural strength. The benefits of the present invention, however, are not dependent upon the precise depth of the dimples. As long as there are enough dimples, and each dimple is deep enough to create a small area of turbulent flow, the benefits of the present invention will be attained. The roughly 50% preference is not a strict or precise figure, and it is not anticipated that precise depth measurements would be made of each dimple 42.

The dimples 42 shown in FIGS. 3 and 4 are not the only type of surface perturbation contemplated by the present invention. Recessed dimples 42 may be used, but raised perturbations also may be used. One example of a pattern of raised surface perturbations is shown in FIGS. 5 and 6. A disc surface 46 is shown with a plurality of raised surface perturbations 48. The raised surface perturbations 48 shown in FIGS. 5 and 6 are cylindrical. As shown in FIG. 6, the height of the raised, cylindrical surface perturbations is roughly comparable to the depth of the recessed dimples 42 shown in FIG. 4. The height 50 of the cylinders 48 is about 50% of the disc thickness.

FIGS. 7 and 8 shown another type of raised surface perturbation, this time a hemispherical protrusion 54 on the surface of the disc 52. As in the prior examples, the surface perturbations cover most of the disc surface 52. Also, the raised, hemispherical perturbations have a height 56 of about 50% of the disc thickness. This measurement is not critical. It is chosen to allow the raised protrusions 54 to extend far enough from the disc surface 52 to produce surface turbulence, while not extending much, if any, beyond the boundary layer created when the disc rotates.

In a preferred embodiment, more than 70% of one side of the disc surface is covered by surface perturbations, either recessed, raised, or some combination of the two. Various shapes may be used for the perturbations, as illustrated, to an extent, in the figures. In addition to the shapes shown, conical surface perturbations (either recessed or raised or a combination) could be used. A mix of different shapes, together with a mix of recessed and raised surface perturbations could be used, though this is not preferred because it might unduly increase manufacturing complexity.

The circular ends of the cylindrical discs of the present invention are large relative to the thickness of the discs. These proportions are illustrated in FIGS. 3-8. In a preferred embodiment, the diameter of the cylindrical discs is at least five times larger than the thickness of the disc. In some configurations, this ratio may be much larger, with the disc diameter sometimes being more than ten times larger than the disc thickness. This type of construction is preferred because it is the large, circular surface area of the disc that contributes to pump performance.

The present invention uses many, discrete surface perturbations, rather than a few long radial ribs or waves. The surface perturbations of the present invention are not arranged in any particular pattern, and do not form radial ridges or rows. Instead, the surface perturbations are spread across the discs in a manner designed to create numerous small areas of turbulence that will collectively create a more adherent, turbulent boundary layer. This result alters the pumping performance of the disc pump.

It should be noted that the first disc 26 differs from the second disc 28, and any other additional discs used, in an important respect. Only the first disc 26 is a full disc. Each additional disc (e.g., the second disc 28 shown in FIGS. 1 and 2) must have a central, coaxial opening to allow flow within the housing 12. The need for such a central, coaxial inlet flow path is what requires the use of connecting pins 30 or other connecting means between the discs. It is possible to make the pump such that the second disc 28 (and additional discs) is attached directly to the drive shaft, but some type of central, coaxial flow path still must be provided through the second disc 28 (or any other additional discs). That result might be achieved by using a series of spokes between a central drive shaft an the main body of the disc, or any other physical configuration that securely connects the disc to the drive shaft while allowing flow along the central, axial direction. The means of connecting the second disc 28 and other discs to the rotational driving force is not critical to the present invention.

Because discs beyond the first disc 26 require some central, coaxial opening, it should be understood that the discs shown in FIGS. 3, 5, and 7 are all first discs 26. These discs are full discs, and are, therefore, configured to be attached directly to the rotational driving member. Second disc 28 (and any other discs that may be used) would have some type of opening, or group of openings in the center of the disc surface. In the configuration shown in FIGS. 1 and 2, the second disc 28 has a central, coaxial opening aligned with the inlet 16. If such a disc were shown standing alone (i.e., in the manner of FIGS. 3, 5, and 7), it would look like an annulus, and not like the solid cylinder of the actual figures. The annulus form of the second disc 28 is not explicitly shown in FIG. 3, 5, or 7, but is a well understood characteristic of existing disc or boundary layer pumps.

While the preceding description is intended to provide an understanding of the present invention, it is to be understood that the present invention is not limited to the disclosed embodiments. To the contrary, the present invention is intended to cover modifications and variations on the structure and methods described above and all other equivalent arrangements that are within the scope and spirit of the following claims. 

1. A pump comprising, a. a generally cylindrical housing formed by a front wall, a back wall, and a peripheral wall, wherein the front wall has a central, coaxial inlet and the peripheral wall has an outlet; b. a disc positioned within the housing, one side of the disc having a plurality of surface perturbations, wherein each surface perturbation covers less than 5% of the surface area of the side of the disc and the plurality of surface perturbations collectively cover at least 50% of the surface area of the side of the disc; and, c. a rotational drive member extending through the back wall of the housing and connected to the disc.
 2. The pump of claim 1, wherein the surface perturbations are recessed.
 3. The pump of claim 2, wherein the depth of the recessed surface perturbations is no more than 50% of the thickness of the disc.
 4. The pump of claim 2, wherein the recessed surface perturbations are generally hemispherical.
 5. The pump of claim 2, wherein the recessed surface perturbations are generally cylindrical.
 6. The pump of claim 2, wherein the recessed surface perturbations are generally conical.
 7. The pump of claim 1, wherein the disc further comprises a second side having a plurality of surface perturbations, wherein each surface perturbation covers less than 5% of the surface area of the second side of the disc and the plurality of surface perturbations collectively cover at least 50% of the surface area of the second side of the disc.
 8. The pump of claim 1, wherein the plurality of surface perturbations includes both raised and recessed perturbations.
 9. The pump of claim 1, wherein the surface perturbations are holes extending fully through the disc.
 10. The pump of claim 1, wherein the surface perturbations are raised.
 11. The pump of claim 10, wherein the raised surface perturbations are generally hemispherical.
 12. The pump of claim 10, wherein the raised surface perturbations are generally cylindrical.
 13. The pump of claim 10, wherein the raised surface perturbations extend outward from the surface of the disc a distance no greater than 50% of the thickness of the disc.
 14. The pump of claim 1, wherein the surface perturbations cover at least 70% of the surface area of one side of the disc.
 15. The pump of claim 1, further comprising a second disc operatively connected to the first disc and having a plurality of surface perturbations on one side, wherein each surface perturbation covers less than 5% of the surface area of one side of the second disc and the plurality of surface perturbation collectively cover at least 50% of the surface area of one side of the second disc.
 16. A pump comprising, a. a generally cylindrical housing formed by a front wall, a back wall, and a peripheral wall, wherein the front wall has a central, coaxial inlet and the peripheral wall has an outlet; b. one or more pairs of discs positioned within the housing, wherein each disc has a plurality of surface perturbations on one side of the disc, each surface perturbation covering less than 5% of the surface area of one side of the disc, and the plurality of surface perturbations collectively covering at least 50% of the surface area of one side of the disc; and, c. a rotational drive shaft extending through a central, coaxial opening in the back wall of the housing and connected to at least one disc.
 17. A pump comprising, a. a generally cylindrical housing formed by a front wall, a back wall, and a peripheral wall, wherein the front wall has a central, coaxial inlet and the peripheral wall has an outlet; b. a disc positioned within the housing, one side of the disc having a plurality of dimples, wherein each dimple covers less than 5% of the surface area of the side of the disc, and the plurality of dimples collectively cover at least 50% of the surface area of the side of the disc; and, c. a rotational drive member extending through the back wall of the housing and connected to the disc.
 18. The pump of claim 17, wherein the depth of the dimples is approximately 50% of the thickness of the disc.
 19. The pump of claim 17, wherein the dimples are generally hemispherical.
 20. The pump of claim 17, wherein the dimples are generally cylindrical.
 21. The pump of claim 17, wherein the dimples are generally conical.
 22. A pump impellor, comprising: a. a cylinder having a diameter and a thickness, wherein the diameter is at least five times larger than the thickness, the cylinder further having, i. a first circular surface configured for attachment to a rotational drive shaft; and, ii. a second circular surface having a plurality of surface perturbations, wherein each surface perturbation covers less than 5% of the second circular surface, and the plurality of surface perturbations collectively cover at least 50% of the second circular surface. 